Process for producing fluorinated alkene and fluorinated alkane

ABSTRACT

A vic-dichloro-fluorinated alkene of the formula: R 1  --CCl═CCl--R 2 , and a fluorinated alkane of the formula: R 1  --CR 3  R 4  --CR 5  R 6  --R 2 , wherein each of R 1  and R 2  independently represents a perfluoroalkyl group or both of R 1  and R 2  form together a perfluoroalkylene group, and R 3 , R 4 , R 5  and R 6  independently represent hydrogen or fluorine, are produced from an inexpensive raw material. More specifically, hexachlorocyclopentadiene is reacted with gaseous chlorine using an antimony catalyst, and then the reaction product is reacted with hydrogen fluoride to give 1,2-dichlorohexafluorocyclopentene. Thus-obtained compound is either (i) hydrogenated, or (ii) treated with a fluorinating agent to substitute the chlorine atoms by fluorine atoms, and then hydrogenated, to give the intended fluorinated alkane.

TECHNICAL FIELD

This invention relates to a novel process for producing avic-dichloro-fluorinated alkene having chlorine atoms bonded to carbonatoms of the unsaturated bond, and a process for preparing a fluorinatedalkane through the vic-dichloro-fluorinated alkene as an intermediate.

BACKGROUND ART

Halogenated hydrocarbons containing fluorine have heretofore been usedas detergents, cooling mediums and others. In recent years, to cope withproblem of the damage of the global environment, internationalrestriction on the use of chlorine-containing fluorinated hydrocarbonsis now being tightened, and thus, there is an increasing demand forsubstitutes therefor. Especially fluorinated alkane derivativescontaining no chlorine attract attention in view of protection of theenvironment because they invite no destruction of the ozone layer.

For example, fluorinated alkanes represented by the following formula:

    R.sup.1 --CR.sup.3 R.sup.4 --CR.sup.5 R.sup.6 --R.sup.2

wherein R¹ and R² independently represent a perfluoroalkyl group or mayform a perfluoroalkylene group together, and R³, R⁴, R⁵ and R⁶independently represent a hydrogen or fluorine atom, are expected widelyfor uses such as detergents, solvents, propellants, heating mediums forheat pumps and others. As specific examples of the fluorinated alkanes,there can be mentioned 1,1,2,2,3,3-hexafluorocyclopentane disclosed asbeing useful for a detergent in U.S. Pat. No. 5,084,199, and1,2,3,3,4,4,5,5-octafluorocyclopentane is disclosed as being useful fora detergent and a desiccating agent in Japanese Patent Application No.5-88022.

Now there is an urgent request for establishment of a process forproducing in a commercial scale fluorinated alkanes as substitutes forthe chlorine-containing fluorinated hydrocarbons. Especially a processfor producing intermediates used for the production of fluorinatedalkanes in a commercial scale and at a reduced cost is eagerly required.Vic-dichloro-fluorinated alkenes having chlorine atoms bonded to thecarbon atoms of the carbon-carbon unsaturation in the molecule and otherfluorinated alkenes are used as intermediates for the production of thefluorinated alkanes. For example, there have been proposed a process forallowing 1,2-dichlorohexafluorocyclopentene to react with hydrogen inthe presence of a palladium or nickel catalyst to yield1,1,2,2,3,3-hexafluorocyclopentane in DE-A 3,735,467 and U.S. Pat. No.5,084,199; a process for treating 1,2-dichlorohexafluorocyclopentenewith a fluorinating agent such as a potassium fluoride to yield afluorine-substituted compound in U.S. Pat. No. 3,024,290; and a processfor allowing said fluorine-substituted compound to react with hydrogenin the presence of a palladium catalyst to yield1,2,3,3,4,4,5,5-octafluorocyclopentane in Japanese Patent ApplicationNo. 5-88022.

As examples of the process for producing vic-dichloro-fluorinatedalkene, there can be mentioned two processes, i.e., a process using aperchloro-olefin and a process using a perchloro-conjugated dienecompound.

As an example of the process using a perchloro-olefin, a process hasbeen proposed in J. Am. Chem. Soc., 67, 1235 (1945) whereinoctachlorocyclopentene is allowed to react with a mixture of antimonytrifluoride and antimonytrifluoro-dichloride to yield1,2-dichlorohexafluorocyclopentene. However, the reaction involved inthis process is stoichiometric, and thus an expensive reagent must beused in a salient amount, and the yield is low, i.e, about 50%.

As another example, a process has been proposed in DE-C 3,935,493wherein octachlorocyclopentene is allowed to react with chlorine andhydrogen fluoride in the presence of antimony pentachloride to yield1,2-dichlorohexafluorocyclopentene. It is described in this patent thatthe antimony pentachloride used is fluorinated by the action of hydrogenfluoride to pentavalent antimony fluoride which has a fluorinatingaction, and, simultaneously with the fluorination, trivalent antimonyproduced as a by-product during the fluorination reaction is reproducedinto pentavalent antimony by the action of chlorine gas, and thus, theantimony compound can be repeatedly used, namely, the reaction can beconducted with a catalytic amount of the antimony compound, and theyield is high. However, octachlorocyclopentene used as the startingmaterial is expensive, and has poor handling properties because it issolid under normal temperature and normal pressure. Therefore, thisprocess is not beneficial for a commercial scale production.

A perchloro-conjugated diene compound, for example,hexachlorocyclopentadiene is liquid under normal temperature and normalpressure and has good handling properties, is used widely as anintermediate for the preparation of pharmaceuticals and pesticides, andis readily commercially available and inexpensive. Thereforehexachlorocyclopentadiene is expected as a raw material for theproduction of a vic-dichloro-fluorinated alkene such as1,2-dichlorohexafluorocyclopentene. For example, there have beenproposed a process wherein hexachlorocyclopentadiene is allowed to reactwith antimony pentafluoride to yield 1,2- dichlorohexafluorocyclopentenein U.S. Pat. No. 2,459,783, and a process whereinhexachlorocyclopentadiene is first reacted with hydrogen fluoride andthen the reaction product is reacted with chlorine gas in the presenceof a catalyzing amount of antimony pentachloride to yield1,2-dichlorohexafluorocyclopentene in U.S. Pat. No. 2,449,233. However,the reaction involved in the former process using antimony pentafluorideis stoichiometric, and therefore, an expensive reagent must be used in asalient amount, and the yield is low, i.e., at most about 40%. Thelatter process, wherein hexachlorocyclopentadiene is first allowed toreact with hydrogen fluoride by using a catalyzing amount of antimonypentachloride, and then allowed to react with chlorine gas, involvesside-reactions and the intended 1,2-dichlorohexafluorocyclopentene isproduced only to a negligible extent. This is in striking contrast tothe process of DE-C 3,935,493 wherein 1,2-dichlorohexafluorocyclopenteneis produced from octachlorocyclopentene.

DISCLOSURE OF THE INVENTION

In view of the foregoing, the inventors have conducted extensiveresearches and found that the reaction of hexachlorocyclopentadiene,which is liquid at normal temperature and pressure and is inexpensive,with chlorine gas in the presence of a catalyzing amount of antimonypentachloride, and then with hydrogen fluoride gives1,2-dichlorohexafluorocyclopentene in good yield, that the reaction ofthe thus-obtained 1,2-dichlorohexafluorocyclopentene with hydrogen usinga palladium catalyst in the presence of triethylamine readily gives1,1,2,2,3,3-hexafluorocyclopentane, and further that, when the1,2-dichlorohexafluorocyclopentene is reacted with potassium fluoride tosubstitute the chlorine atoms to fluorine atoms, and then the reactionproduct is reacted with hydrogen in the presence of a palladiumcatalyst, 1,2,3,3,4,4,5,5-octafluorocyclopentane is readily obtained.Based on these findings, the present invention has been completed.

In accordance with the present invention, there are provided (1) aprocess for producing a vic-dichloro-fluorinated alkene represented bythe following formula:

    R.sup.1 --CCl═CCl--R.sup.2

which comprises allowing a perchloro-conjugated diene compound to reactwith chlorine in the presence of an antimony catalyst, and then allowingthe reaction product to react with hydrogen fluoride;

(2) a process for producing a fluorinated alkane represented by thefollowing formula:

    R.sup.1 --CH.sub.2 --CH.sub.2 --R.sup.2

which comprises allowing a perchloro-conjugated diene compound to reactwith chlorine in the presence of an antimony catalyst, allowing thereaction product to react with hydrogen fluoride, and then allowing thethus-prepared vic-dichloro-fluorinated alkene to react with hydrogen inthe presence of a hydrogenation catalyst and in the co-presence of abasic compound; and

(3) a process for producing a fluorinated alkane represented by thefollowing formula:

    R.sup.1 --CHF--CHF--R.sup.2

which comprises allowing a perchloro-conjugated diene compound to reactwith chlorine in the presence of an antimony catalyst, allowing thereaction product to react with hydrogen fluoride, allowing thethus-prepared vic-dichloro-fluorinated alkene to react with afluorinating agent to substitute the chlorine atoms of thevic-dichloro-fluorinated alkene to fluorine atoms, and then allowing thethus-prepared fluorinated alkene to react with hydrogen in the presenceof a hydrogenation catalyst.

BEST MODE FOR CARRYING OUT THE INVENTION

In the above-recited formulae, each of R¹ and R² independentlyrepresents a perfluoroalkyl group or both of R¹ and R² form together aperfluoroalkylene group. The number of carbons in each of R¹ and R² isnot particularly limited, but is usually not larger than 20, preferably1 to 10, and more preferably 1 to 4. As specific examples of theperfluoroalkyl group, there can be mention trifluoromethyl,pentafluoroethyl, heptafluoropropyl, heptafluoroisopropyl,nonafluorobutyl, nonafluoroisobutyl, undecafluoropentyl,tridecafluorohexyl, heptadecafluorooctyl, perfluorododecyl,perfluorotetradecyl, perfluorohexadecyl and perfluorooctadecyl. Asspecific examples of the perfluoroalkylene group, there can bementioned, difluoromethylene, tetrafluoroethylene, hexafluoropropylene,octafluorobutylene, decafluoropentylene and dodecafluorohexylene. R¹ andR² should not be construed to mean limitedly only to these examples.

The main feature of the present invention lies in a reaction routewherein a perchloro-conjugated diene compound is first allowed to reactwith chlorine in the presence of an antimony catalyst, and then thereaction product is allowed to react with hydrogen fluoride. Ifhexachlorocyclopentadiene, which is a perchloro-conjugated dienecompound, is first allowed to react with hydrogen fluoride, and then thereaction product is allowed to react with chlorine as described in U.S.Pat. No. 2,449,233, then salient amounts of by-products are produced andthe intended 1,2-dichlorohexafluorocyclopentene is produced only in alimited amount. If a perchloro-conjugated diene compound is allowed toreact with hydrogen fluoride and chlorine at the same time, similarlysalient amounts of by-products are produced and the intended1,2-dichlorohexafluorocyclopentene is produced only in a limited amount.

The present invention will now be described in detail.

The perchloro-conjugated diene compound used in the present invention isnot particularly limited, and includes, for example, aliphaticperchloro-compounds such as hexachlorobutadiene, octachloropentadiene,decachlorohexadiene and tetradecachlorooctadiene, and alicyclicperchloro-compound such as hexachlorocyclopentadiene,octachlorocyclohexadiene, and dodecachlorocyclooctadiene. Of these,hexachlorobutadiene and hexachlorocyclopentadiene are preferably used.These perchloro-conjugated diene compounds can be easily produced in alarge scale and a good yield by a process wherein a conjugated dienehydrocarbon compound such as cyclopentadiene is allowed to react withgaseous chlorine as described in, for example, GB Patent 1,070,891.

The antimony catalyst used in the present invention is not particularlylimited, and those which are conventionally used for ordinary reactionscan be used. As specific examples of the antimony catalyst, there can bementioned anitmony fluorides such as antimony trifluoride and antimonypentafluoride, antimony chlorides such as antimony trichloride andantimony pentachloride, antimony mixed halides such as antimonytrifluoro-dichloride, other antimony halides such as antimony tribromideand antimony triiodide, and antimony oxides such as antimony trioxide.Of these, antimony chlorides are preferable in view of enhanced catalystactivity and inexpensiveness. These catalysts may be used either aloneor in combination.

The amount of the catalyst is not particularly limited, and variesdepending upon the reaction conditions. The amount of the catalyst isusually 0.01 to 20 moles, preferably 0.1 to 10 moles and more preferably0.5 to 5 moles, per mole of the perchloro-conjugated diene compound. Ifthe amount of the catalyst is too small, the reaction time becomesunreasonably long and the degree of fluorination is lowered. Incontrast, the use of an excessively large amount of catalyst is notadvantageous for cost consideration. The antimony catalyst is verystable and is deactivated only to a negligible extent under the reactionconditions employed in the process of the invention, and, after thereaction product is removed by distillation, the catalyst can besuccessively reused merely by incorporating a starting compound.

A diluent can be used in the process of the present invention, ifdesired. The diluent used is not particularly limited provided that itis stable under the reaction conditions employed. As examples of thediluent, there can be mentioned aliphatic hydrocarbons such as n-pentaneand n-hexane, alicyclic hydrocarbons such as cyclopentane andcyclohexane, aromatic hydrocarbons such as benzene and toluene, andperfluoroalkanes such as perfluorohexane, perfluoroheptane andperfluorodecalin. Of these, aliphatic hydrocarbons and alicyclichydrocarbons are preferable. Instead of the perchloro-conjugated dienecompound, intermediates for the intended vic-dichloro-fluorinated alkenederivatives can also be used, which include, for example,trichloropentafluorocyclopentene and tetrachlorotetrafluorocyclopentene.

The amount of gaseous chlorine, which is incorporated in a mixture ofthe starting compound, i.e., a perchloro-conjugated diene compound, andan antimony catalyst, is usually at least equimolar to the sum of thestarting compound and the catalyst, and preferably 1 to 10 moles, morepreferably 1 to 5 moles, per mole of the sum of the starting compoundand the catalyst. However, when antimony pentachloride is used as thecatalyst, the amount of gaseous chlorine should be at least equimolar tothe starting compound. The reaction pressure is not higher than 10kg/cm², preferably -0.5 to 6 kg/cm², as the gauge pressure. The reactiontemperature may not necessarily be controlled, but, to ensure safetyfrom heat evolved during the reaction and to prevent deterioration ofthe catalyst, the reaction temperature is usually controlled to atemperature of 20° to 200° C., preferably 60° to 150° C. and morepreferably 80° to 120° C.

Hydrogen fluoride is not particularly limited provided that it can beused for ordinary chemical reactions, but, anhydrous hydrogen fluorideis preferably used to prevent hydrolysis of the catalyst and corrosionof an apparatus. The amount of hydrogen fluoride is usually at least 6moles, preferably 6 to 20 moles, per mole of the starting compound.

The reaction conditions employed in the fluorination step are notparticularly limited, but, since hydrogen chloride gas is evolved inthis step, it is preferable for enhancing the reaction efficiency thatan equipment provided with a reflux condensing cooling apparatus and apressure-keeping valve is employed and the reaction pressure ismaintained at a pressure higher than the vapor pressure of hydrogenfluoride to discharge hydrogen chloride gas from the reactor whileavoiding the loss of hydrogen fluoride. The reaction pressure is usuallyin the range of 1 to 30 kg/cm², preferably 3 to 20 kg/cm² and morepreferably 5 to 15 kg/cm². If the reaction pressure is too low, hydrogenfluoride is undesirably discharged and the degree of fluorination isreduced. In contrast, if the reaction pressure is too high, the removalof hydrogen chloride gas from the reaction system becomes difficult andthe yield of the vic-dichloro-fluorinated alkene is lowered. Thereaction temperature is usually in the range of 20° to 200° C.,preferably 60° to 160° C. and more preferably 80° to 120° C. If thereaction temperature is too high, stability of the antimony catalyst isreduced. In contrast, if the reaction temperature is too low, the rateof reaction decreases. The reaction time varies depending upon theparticular reaction pressure and reaction temperature, but is usuallywithin 48 hours preferably in the range of 1 to 10 hours.

After the completion of evolution of hydrogen chloride gas, the residualhydrogen fluoride is removed and the reaction mixture can be aged.Namely, the pressure is restored to normal pressure and the reactionmixture is maintained at a reaction temperature of 20° to 200° C.,preferably 60° to 160° C. and more preferably 80° to 140° C. Thereaction time is usually within 20 hours and preferably 2 to 10 hours.When the reaction temperature is maintained at a temperature higher thanthe boiling point of the reaction product, usually in the range of 80°to 200° C., and preferably 120° to 140° C., distillation of the reactionproduct can be conducted simultaneously with proceeding of the reaction.

After the completion of reaction, the residual hydrogen fluoride isremoved and the reaction mixture is distilled to give the intendedreaction product. If desired, the product is fractionated thereby to bepurified. The catalyst can be reused, and thus, after the removal of thereaction product by distillation, a raw material can be incorporated torepeat the reaction.

The thus-prepared vic-dichloro-fluorinated alkene is allowed to reactwith hydrogen by the conventional procedure using a hydrogenationcatalyst in the presence of a basic compound to give a fluorinatedalkane represented by the following formula:

    R.sup.1 --CH.sub.2 CH.sub.2 --R.sup.2

wherein R¹ and R² are as defined above.

The basic compounds include organic basic compounds and inorganic basiccompounds. As specific examples of the organic basic compounds, therecan be mentioned organic carboxylic acid salts such as sodium formate,sodium acetate, potassium acetate, calcium acetate, sodium propionate,sodium butyrate and sodium valerate; carbonic acid salts such as sodiumcarbonate, potassium carbonate, lithium carbonate, magnesium carbonate,calcium carbonate, barium carbonate, sodium hydrogencarbonate andpotassium hydrogencarbonate; and hydroxides such as sodium hydroxide,potassium hydroxide, calcium hydroxide, barium hydroxide and magnesiumhydroxide. As specific examples of the inorganic basic compounds, therecan be mentioned aliphatic amines such as ethylamine, diethylamine,ethanolamine, diethanolamine, triethanolamine, trimethylamine,triethylamine and diisopropylethylamine; aromatic amines such as2-lutidine, aniline, N-methylaniline, N,N-dimethylaniline andN,N-diethylaniline; and heterocyclic amines such as4-dimethylaminopyridine, pyridine, piperidine, pyrrolidine,N-methylpiperidine, N-methylmorpholine and N-ethylmorpholine. Among theinorganic basic compounds, alkali metal salts of organic carboxylicacids, alkali metal salts of carbonic acid and alkali metal hydroxidesare preferable. Alkali metal hydroxides are most preferable. Among theorganic basic compounds, aliphatic amines and heterocyclic amines arepreferable. Aliphatic amines are most preferable. The amount of thebasic compound is not particularly limited and varies depending upon theparticular reaction conditions. Usually the amount of the basic compoundis at least one mole, preferably 1 to 10 moles and more preferably 1 to5 moles, per mole of the alcohol used.

The hydrogenation catalyst used is not particularly limited, andincludes heterogeneous catalysts and homogeneous catalysts, which areconventionally used for hydrogenation of alkenes. As examples of theheterogeneous catalysts, there can be mentioned solid catalyst comprisedof a metal of group 8 of the periodic table such as nickel, palladium orplatinum, and solid catalyst comprised of a metal of group 8 of theperiodic table, supported on a support such as carbon, silica,diatomaceous earth, alumina or titanium oxide. The solid catalystincludes, for example, those which are a combination of a nickel orcobalt compound with an organic compound of a metal of group 1 to 3 ofthe periodic table, such as nickel naphthenate/triethyl-aluminum, nickeloctenoate/n-butyllithium and nickel acetyl-acetonate/triethyl aluminum.In the case where the hydrogenation product is purified by distillationimmediately after completion of the hydrogenation reaction, aheterogeneous catalyst is preferably used because it can easily beseparated. The amount of the catalyst is suitably selected within therange of 10⁻⁶ to 10% by weight, preferably 10⁻⁵ to 10³¹ 2 % by weight,based on the weight of the vic-dichloro-fluorinated alkene.

If desired, a solvent can be used as a reaction medium in thehydrogenation reaction. The solvent is not particularly limited providedthat it is inert to the reaction. As specific examples of the solvent,there can be mentioned alcohols such as ethanol, methanol andisopropanol; aliphatic hydrocarbons such as n-pentane and n-hexane;alicyclic hydrocarbons such as cyclopentane and cyclohexane; esters suchas ethyl acetate and butyl acetate; ethers such as diethyl ether,tetrahydrofuran and 1,4-dioxane; and ketones such as methyl ethylketone.

The reaction conditions are not particularly limited and vary dependingthe particular raw materials and reaction apparatus employed. Usuallythe reaction temperature is 0° to 200° C. and preferably 20° to 150° C.,and the reaction time is 0.1 to 15 hours and preferably 0.5 to 10 hours.Although the reaction pressure varies depending upon the particular rawmaterials and the reaction temperature, usually the hydrogenationreaction is carried out at a pressure of about 1 to 50 kg/cm² in aclosed reaction vessel.

After the completion of the hydrogenation reaction, the hydrogenationcatalyst used is removed from the liquid reaction mixture and the liquidreaction mixture is distilled whereby a fluorinated alkane can beisolated.

The vic-dichloro-fluorinated alkene is allowed to react with afluorinating agent by the conventional procedure to substitute thechlorine atoms of the vic-dichloro-fluorinated alkene by fluorine atoms,and then the thus-prepared fluorinated alkene is allowed to react withhydrogen in the presence of a hydrogenation catalyst to give afluorinated alkane represented by the following formula:

    R.sup.1 --CHFCHF--R.sup.2

wherein R¹ and R² are as defined above.

The fluorinating agent used is not particularly limited and includesthose which are conventionally used for substituting the chlorine atomsor bromine atoms of an alkane or alkene by fluorine atoms. As specificexamples of the fluorinating agent, there can be mentioned alkali metalfluorides such as lithium fluoride, sodium fluoride, potassium fluoride,cesium fluoride and rubidium fluoride. Of these, potassium fluoride andcesium fluoride are preferable. The amount of the fluorinating agent isusually at least one mole, preferably 1 to 10 moles and more preferably1 to 5 moles, per mole of the starting vic-dichloro-fluorinated alkene.If desired, a solvent can be used in the reaction medium in thefluorinating reaction. As specific examples of the solvent, there can bementioned acid amides such as formamide, acetamide, dimethylformamide,dimethylacetamide and N-methylpyrrolidone, and sulfoxides such asdimethylsulfoxide and diethylsulfoxide. If desired, a compatiblehydrocarbon such as xylene can be added to the solvent used. Thereaction temperature is usually not higher than 200° C., preferably inthe range of 60° to 180° C. and more preferably 80° to 140° C., and thereaction time is suitably selected depending upon the particularfluorinating agent and is usually within 24 hours.

The hydrogenation of the fluorinated alkene and the isolation of theresulting fluorinated alkane can be conducted by the same procedures asmentioned above.

The invention will now be specifically described by the followingexamples that by no means limit the scope of the invention.

EXAMPLE 1

A 0.7 liter-volume stainless steel reactor provided with a coolingreflux condenser and a pressure-keeping valve was charged with 95 g ofantimony pentachloride and 33 g of hexachlorocyclopentadiene, and 10 gof chlorine gas was introduced at a pressure of 5 kg/cm² and atemperature of 80° C. to conduct chlorination for 2 hours. After theresidual chlorine gas was discharged, 21 g of anhydrous hydrogenfluoride was added to conduct fluorination at 84° C. and 7 kg/cm² whilehydrogen chloride gas produced is discharged through thepressure-keeping valve. After the completion of evolution of hydrogenchloride gas, the pressure was lowered to normal pressure and theresidual hydrogen fluoride was removed, and the reaction was continuedat 140° C. and normal pressure further for 5 hours. During the reaction,a fraction boiling at 70° to 110° C. was collected and neutralized withaqueous sodium bicarbonate to give 29.5 g of a crude product. Gaschromatography analysis of the product revealed that 28 g to theintended 1,2-dichlorohexachloropentene was obtained (yield: 95%).

Comparative Example 1

The same procedures as described in Example 1 were repeated except thatthe order of application of the reactants was changed, i.e.,hexachlorocyclopentadiene was allowed to first react with hydrogenfluoride and then react with chlorine. The intended1,2-dichlorohexachloropentene was obtained only in a negligible amount,and, 41% of 1,2,4-trichloro-3,3,5,5-tetrafluorocyclopentene and 33% ofan mixture of trifluoro-isomers were obtained as by-products.

Comparative Example 2

The same procedures as described in Example 1 were repeated except thatchlorine gas and hydrogen fluoride were simultaneously charged into thereactor and, after the reactor was closed, a reaction was conducted at150° C. The intended 1,2-dichlorohexachloropentene could not beobtained, and, 16.1% of a tetrafluoro-isomer mixture, 35.6% of atrifluoro-isomer mixture and 35.6% of a difluoro-isomer mixture wereobtained as by-products.

EXAMPLE 2

In this example, a catalyst was repeatedly used.

First use

A 0.7 liter-volume stainless steel reactor provided with a coolingreflux condenser and a pressure-keeping valve was charged with 95 g ofantimony pentachloride and 140 g of hexachlorocyclopentadiene, and 39 gof chlorine gas was introduced at a pressure of 5 kg/cm² and atemperature of 80° C. to conduct chlorination for 2 hours. Then, 210 gof anhydrous hydrogen fluoride was added to conduct fluorination at 100°C. and 10 kg/cm² while hydrogen chloride gas produced is dischargedthrough the pressure-keeping valve. After the completion of hydrogenchloride gas, the pressure was lowered to normal pressure and theresidual hydrogen fluoride was removed, and the reaction was continuedat 140° C. and normal pressure further for 5 hours. During the reaction,a fraction boiling at 70° to 110° C. was collected and neutralized withaqueous sodium bicarbonate to give 127 g of a crude product. Gaschromatography analysis of the product revealed that 107.5 g (yield,86%) of the intended 1,2-dichlorohexachloropentene was obtained.

Second use

Into the reactor containing the distillation residue, 140 g ofhexachlorocyclopentadiene was newly added and the reaction was conductedby the same procedures as described above with respect to the first useof the catalyst. 101.7 g of a crude product and 93.3 g (yield, 74%) ofthe intended 1,2-dichlorohexachloropentene were obtained. Thus it wasfound that the catalyst was deactivated only to a small extent duringthe second use, and could repeatedly be used.

EXAMPLE 3

The same procedures as described in Example 1 were repeated except thathexachlorobutadiene was used instead of hexachlorocyclopentadiene. Theintended 2,3-dichlorohexafluoro-2-butene was obtained in a good yield.

EXAMPLE 4

A 1 liter-volume reactor was charged with 23.2 g of potassium fluorideand 400 ml of N-methylpyrrolidone, and the content was heated to 200° C.24.5 g of 1,2-dichlorohexafluorocyclopentene obtained in Example 1 wasadded dropwise over a period of 3 hours, and the mixture was maintainedat 200° C. for 8 hours to conduct distillation to give 14.9 g (yield,70%) of octafluorocyclopentene (b.p., 27° C.).

Then a reactor was charged with 12 g of the octafluorocyclopentene and0.24 g of a 5%-palladium/carbon catalyst and hydrogenation was conductedat a temperature of 50° C. and a hydrogenation pressure of 6 kg/cm².When the absorption of hydrogen ceased, the reaction was completed.After the removal of the catalyst and the produced hydrogen fluoridefrom the reaction mixture, the reaction mixture was distilled to give 9g of 1,2,3,3,4,4,5,5-octafluorocyclopentane (b.p., 79° C.; purity, 99%).

EXAMPLE 5

A stainless steel reactor, the inner wall of which was lined with afluoroplastic, was charged with 5.0 g of1,2-dichlorohexafluorocyclopentene, 0.1 g of a 5%-palladium/carboncatalyst and 4.1 g of triethylamine, and hydrogen gas was introduced toa pressure of 5 kg/cm². The mixture was heated to 40° C. while beingstirred, and the reaction was conducted while the hyfrogen consumed wassupplemented. After 7 hours' reaction, it was confirmed that theconsumption of hydrogen ceased. Then the catalyst was removed from thereaction mixture and the reaction mixture was distilled to give 4.2 g of1,1,2,2,3,3-hexafluorocyclopentane (b.p., 84.5-85° C. ).

INDUSTRIAL APPLICABILITY

By the practice of the present invention, a perchloroconjugated dienecompound such as hexachlorocyclopentadinene, which is liquid at normaltemperature and pressure and is inexpensive, can be converted to acorresponding vic-dichlorofluorinated alkene in a good yield and in acommercial scale. The vic-dichloro-fluorinated alkene is either (i)hydrogenated, or (ii) is treated with a fluorinating agent to substitutethe chlorine atoms to fluorine atoms, and then the thus-obtainedfluorinated alkene is hydrogenated, whereby a fluorinated alkane can beobtained in a commercial scale.

The thus-obtained fluorinated alkenes and fluorinated alkanes are usefulas substitutes for chlorine-containing fluorinated hydrocarbons orintermediates for the preparation thereof, and raw materials for thesynthesis of pharmaceuticals, pesticides, liquid crystals and polymers.

We claim:
 1. A process for producing a vic-dichloro-fluorinated alkenerepresented by the following formula:

    R.sup.1 --CCl═CCl--R.sup.2

wherein each of R¹ and R² independently represents a perfluoroalkylgroup or both of R¹ and R² form together a perfluoroalkylene group,characterized by the steps of: allowing a perchloro-conjugated dienecompound to react with chlorine in the presence of an antimony catalystand in the absence of hydrogen fluoride, and then allowing the reactionproduct to react with hydrogen fluoride.
 2. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein, aftercompletion of the reaction with hydrogen fluoride, an excessive amountof hydrogen fluoride is removed from the reaction mixture and thereaction product is distilled off, and thereafter, aperchloro-conjugated diene compound is newly added to the distillationresidue to successively repeat the reactions for the production of thevic-dichloro-fluorinated alkene.
 3. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein thechlorination reaction is conducted at a temperature of 20° to 200° C.and a pressure not higher than 10 kg/cm².
 4. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein thereaction with hydrogen fluoride is conducted at a temperature equal toor higher than the boiling point of the reaction product.
 5. A processfor producing the vic-dichloro-fluorinated alkene according to claim 1,wherein the reaction with hydrogen fluoride is conducted at atemperature of 20° to 200° C.
 6. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein theperchloro-conjugated diene compound is hexachlorobutadiene orhexachlorocyclopentadiene.
 7. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein the amountof the antimony catalyst is in the range of 0.01 to 20 moles per mole ofthe perchloro-conjugated diene compound.
 8. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein theantimony catalyst is an antomony halide.
 9. A process for producing thevic-dichloro-fluorinated alkene according to claim 8, wherein theantimony halide is antimony chloride.
 10. A process for producing thevic-dichloro-fluorinated alkene according to claim 1, wherein thehydrogen fluoride is anhydrous hydrogen fluoride.
 11. A process forproducing a fluorinated alkane represented by the following formula:

    R.sup.1 --CH.sub.2 --CH.sub.2 --R.sup.2

wherein each of R¹ and R² independently represents a perfluoroalkylgroup or both of R¹ and R² form together a perfluoroalkylene group,characterized by the steps of: allowing a perchloro-conjugated dienecompound to react with chlorine in the presence of an antimony catalystand in the absence of hydrogen fluoride, allowing the thus-preparedreaction product to react with hydrogen fluoride to give avic-dichlorofluorinated alkene represented by the follow formula:

    R.sup.1 --CCl═CCl--R.sup.2

wherein R¹ and R² are as defined above, and then allowing thevic-dichloro-fluorinated alkene to react with hydrogen in the presenceof a hydrogenation catalyst and in the co-presence of a basic compound.12. A process for producing the fluorinated alkane according to claim11, wherein, after completion of the reaction of the reaction productprepared in the first step with hydrogen fluoride, an excessive amountof hydrogen fluoride is removed from the reaction mixture and thereaction product is distilled off, and thereafter, aperchloro-conjugated diene compound is newly added to the distillationresidue to successively repeat the reactions for the production of thevic-dichloro-fluorinated alkene.
 13. A process for producing thefluorinated alkane according to claim 11, wherein theperchloro-conjugated diene compound is hexachlorocyclopentadiene orhexachloropentadiene.
 14. A process for producing the fluorinated alkaneaccording to claim 11, wherein the basic compound is an amine compoundor a basic alkali metal salt.
 15. A process for producing thefluorinated alkane according to claim 11, wherein the hydrogenationcatalyst is heterogeneous catalyst or a homogeneous catalyst.
 16. Aprocess for producing the fluorinated alkane according to claim 11,wherein the hydrogenation catalyst is heterogeneous catalyst.
 17. Aprocess for producing the fluorinated alkane according to claim 16,wherein the heterogeneous catalyst is a catalyst of a metal selectedfrom the group consisting of metals of group 8 of the periodic table.18. A process for producing a fluorinated alkane represented by thefollowing formula:

    R.sup.1 --CHF--CHF--R.sup.2

wherein each of R¹ and R² independently represents a perfluoroalkylgroup or both of R¹ and R² form together a perfluoroalkylene group,characterized by the steps of: allowing a perchloro-conjugated dienecompound to react with chlorine in the presence of an antimony catalystand in the absence of hydrogen fluoride, allowing the thus-preparedreaction product to react with hydrogen fluoride to give avic-dichloro-fluorinated alkene represented by the following formula:

    R.sup.1 --CCl═CCl--R.sup.2

wherein R¹ and R² are as defined above, allowing thevic-dichloro-fluorinated alkene to react with a fluorinating agent tosubstitute the chlorine atoms of the vic-dichloro-fluorinated alkene byfluorine atoms, and then allowing the thus-prepared fluorinated alkeneto react with hydrogen in the presence of a hydrogenation catalyst. 19.A process for producing the fluorinated alkane according to claim 18,wherein, after completion of the reaction of the reaction productprepared in the first step with hydrogen fluoride, an excessive amountof hydrogen fluoride is removed from the reaction mixture and thereaction product is distilled off, and thereafter, aperchloro-conjugated diene compound is newly added to the distillationresidue to successively repeat the reactions for the production of thevic-dichloro-fluorinated alkene.
 20. A process for producing thefluorinated alkane according to claim 18, wherein theperchloro-conjugated diene compound is hexachlorobutadiene orhexachlorocyclopentadiene.
 21. A process for producing the fluorinatedalkane according to claim 18, wherein the fluorinating agent is analkali metal fluoride.
 22. A process for producing the fluorinatedalkane according to claim 18, wherein the hydrogenation catalyst isheterogeneous catalyst or a homogeneous catalyst.
 23. A process forproducing the fluorinated alkane according to claim 22, wherein thehydrogenation catalyst is heterogeneous catalyst.
 24. A process forproducing the fluorinated alkane according to claim 23, wherein theheterogeneous catalyst is a catalyst of a metal selected from the groupconsisting of metals of group 8 of the periodic table.